JP5384670B2 - Aircraft engine with electric starter cooling - Google Patents

Description

  The present invention relates to cooling an electrical device for starting an aero engine.

  A particular field of application of the invention is in the field of aircraft engines with gas turbines, in particular turbo engines.

  The start of the aero engine is usually ensured by an electric machine that drives the shaft of the engine. The electric machine may be a motor or machine that forms a starter / generator (or S / G) that operates in motor mode when started and then in synchronous generator mode.

  An electronic power supply that is used when starting, for example as shown in EP 1953899, by an electric starter, ie by an actual electric machine, and preferably also for controlling the electric machine It is necessary to remove the amount of heat generated by the circuit.

  In aero engines, fuel is typically used as a cooling fluid, either directly or by heat exchange with a heat transfer fluid, such as oil.

  Fuel is pumped into the tank and delivered to the engine's fuel circuit with a high pressure pump. The high pressure pump delivers fuel under high pressure to the main circuit for supply to the combustion chamber of the engine. The high-pressure pump is usually a gear pump driven from the shaft of the engine via a mechanical transmission box or an accessory gear box AGB.

  It has been proposed to ensure cooling of the electric starter by the fuel received at the outlet of the high pressure pump of the engine pumping circuit. In order to ensure a sufficient flow of coolant fuel at a low starting speed, it is necessary to give the high pressure pump considerable capacity. In that case, such capacity is generally oversized to provide the flow required by the main supply circuit while the engine is operating at rated speed, thereby returning the fuel to a low pressure. Divert a significant portion of the fuel provided by the high pressure pump. The use of an additional pump that is mechanically driven by the engine to supply the cooling device of the electric starter may be considered. However, such a solution is represented by an increase in mass and the requirement for an additional mechanical connection with the AGB, which then causes problems at high speed by diverting excessive fuel flow.

  U.S. Pat. No. 3,733,816 uses a fuel provided by a pump in series with a high pressure fuel pump located upstream of a high pressure fuel pump to cool a gas turbine engine computer. Proposed, both pumps are mounted on a common drive shaft coupled to the engine.

European Patent No. 1953899 US Pat. No. 3,733,816

  The object of the present invention is to propose a solution to the problem of cooling electric starters which does not have such drawbacks.

  The purpose of this is by means of a fuel pumping device comprising a high pressure pump having an inlet connected to a low pressure fuel conduit and an outlet connected to a main circuit for supplying high pressure fuel, an electrical device for starting the engine, and fuel circulation. An aero engine comprising a cooling device for an electric starter connected to a pumping device to ensure cooling, the cooling device being driven by an electric motor independently of the high-pressure pump and This is accomplished using an aero engine, fueled by a pump having an inlet connected to a pumping device upstream of the high pressure pump.

  The use of such an electric pump offers the possibility of ensuring sufficient flow of cooling fuel at low speed without increasing the capacity of the high pressure pump, which is bulky compared to adding a pump mechanically driven by the engine. And is not complicated.

  Advantageously, the pumping device comprises a low-pressure pump driven from the shaft of the engine and having an outlet connected to the inlet of the high-pressure pump, the electric pump supplying the cooling device being Having an inlet connected to the pumping device between the outlet and the inlet of the high pressure pump;

  Thus, after starting, the electric pump may be disabled when the engine speed increases, in which case the low pressure pump is driven at a sufficient speed to effectively supply the cooling device. Cooling may be permanently required when the electrical starter is of the S / G type.

  More advantageously, the electric pump supplying the cooling device has an outlet connected to the main circuit for supplying high pressure fuel.

  Thus, during the startup phase, the electric pump can contribute to providing sufficient fuel flow to the main fuel supply circuit. In that case, it is possible to use a high-pressure pump that is a gear type but has a small capacity, or a centrifugal high-pressure pump that is smaller in mass and more reliable than a gear pump. Deliver lower fuel flow at start speed.

  According to one particular embodiment, the cooling device circulates fuel, connected to the first circuit for circulating the heat transfer fluid connected to the electric starter and to the electric pump supplying the cooling device. And a heat exchanger inserted through the first circuit and the second circuit.

  The cooling device may be designed to cool the electric starter of the electric starter and the power control circuit of the electric starter.

  The invention will be better understood upon reading the description given below, which is indicative and not limiting, with reference to the accompanying drawings.

1 is a schematic diagram of an aviation gas turbine engine. It is a figure which shows one Embodiment of this invention.

  Although the field of application of the present invention is that of aviation gas turbine engines, as shown very schematically in FIG. 1, the present invention applies to other aviation engines, in particular helicopter turbines as well as landborne engines. It is also applicable to an engine) and a marine engine.

  The engine shown in FIG. 1 includes a combustion chamber 1, and combustion gas from the combustion chamber 1 drives a high-pressure turbine 2 and a low-pressure turbine 3. The turbine 2 is connected via a shaft to a high pressure compressor that supplies pressurized air to the combustion chamber, and the low pressure turbine is connected via a separate shaft to a fan 5 at the inlet of the engine. .

  A transmission box or accessory gear box AGB 7 is connected to the turbine shaft via a mechanical power take-off device 9 and comprises a gear assembly for mechanical coupling with a certain number of accessories.

  FIG. 2 is a schematic diagram that prominently shows an engine portion according to an embodiment of the present invention.

  Reference numeral 10 indicates an aircraft fuel tank with a fuel pump 12 that is driven by an electric motor 14 and that feeds a conduit 16 that carries fuel to an engine 20. A low pressure shut-off valve 18 (or LPSOV) is interposed in the conduit 16 upstream of the engine 20.

  The engine 20 includes a pumping device 22 that supplies fuel to a main circuit for supplying high-pressure fuel to a combustion chamber of the engine.

  For this purpose, the pumping device 22 comprises a low-pressure fuel pump 24, the inlet of the low-pressure fuel pump 24 is connected to the conduit 16, and the outlet of the low-pressure fuel pump 24 is connected to the inlet of the high-pressure fuel pump 26 via the conduit 28. Is done. The outlet of the high pressure pump 26 is connected to a conduit 30 of the main supply circuit. The metering device 32 receives a flow of fuel supplied by a high pressure pump to supply a controlled flow of high pressure fuel to a combustion chamber (not shown) of the engine.

  The low-pressure pump 24 is, for example, a centrifugal pump that is mechanically driven via an AGB. In this case, the high-pressure pump 26 is also a gear pump that is mechanically driven via the AGB.

  The engine 20 includes an S / G type electric starter 40, for example. The device 40 is accommodated in the case 42. The device 40 includes an electric machine 44 having a shaft 46 protruding from a case 42 for mechanically coupling with the AGB. In the start-up phase, the electric machine operates in motor mode to drive the turbine shaft via the AGB, but after start-up, when the turbine shaft reaches a sufficient rotational speed, the electric machine operates in generator mode. Can be switched to. The casing 48 accommodates electric power electronics for controlling the electric machine 44. The casing is electrically connected to an electronic control circuit (not shown) of the engine. The casing 48 may be attached to the case 42 as shown, or may be independent of the case 42.

  According to the present invention, the cooling of the electric starter 40 is ensured by the fuel taken into the pumping device by the pump 50 driven by the motor 52 itself, which is controlled by the engine's electronic control circuit, and thus the pump 50 Is independent of the drive of the high-pressure pump 26.

  In the illustrated embodiment, cooling is ensured by heat exchange where the heat transfer fluid absorbs the amount of heat in the starter 40.

  A channel for circulating the heat transfer fluid 42 a is formed in the wall of the case 42 adjacent to the casing 48. A heat transfer fluid is an oil that is also used to lubricate various components including, for example, AGB. An oil circuit with an oil pump (not shown) circulates in the conduit 54 leading oil to the channel 42a and in the channel 42a and, if necessary, lubricates the bearings that support the shaft 46 of the case 42. A conduit 56 for collecting the oil used.

  Heat exchange between fuel and oil is accomplished in exchanger 58. The exchanger 58 receives oil from the starter 40 via a conduit 56 and has an internal oil circuit that returns the cooled oil to the oil circuit, an inlet connected to the outlet of the pump 50 and an outlet connected to the tank 10. And an internal fuel circuit which is a part of the fuel circuit 60 having the same.

  In the illustrated embodiment, the inlet of pump 50 is connected to conduit 28, that is, between the outlet of low pressure pump 24 and the inlet of high pressure pump 26. Thus, the electric pump 50 may be turned off after starting and the rotational speed of the turbine shaft driving the low pressure pump 24 is required to effectively cool the starting device after switching the machine 44 to generator mode. Enough to provide the cooling fuel flow rate. Stopping the pump 50 is controlled by disabling the motor 52 under the control of the engine's electronic control unit when the turbine shaft rotational speed exceeds a given minimum value.

  If only the pumping device comprises a high pressure pump that is directly supplied by the fuel pump of the tank 10, the electric pump 50 is connected to a conduit that supplies the high pressure pump.

  As shown in FIG. 2, the outlet of the electric pump 50 may also be connected via a conduit 62 to the main circuit conduit 30 for supplying pressurized fuel upstream of the metering device 32. Thus, during the startup phase, the pump 50 can contribute to providing sufficient fuel flow to the combustion chamber. This requirement of providing sufficient fuel flow during start-up is no longer a burden on the high-pressure pump 26, so in this case it is advantageously possible to use a centrifugal pump instead of a positive displacement gear pump as the high-pressure pump 26. . An anti-return valve 64 is attached to the conduit 62 to avoid fuel from the high pressure pump 26 flowing into the conduit 62 after startup.

  In the above, it has been considered to cool the starter in an indirect manner with fuel via oil acting as a heat transfer fluid. Of course, other heat transfer fluids can be used, and it is also possible to achieve direct cooling of the starter with fuel by circulating the fuel within the starter.

Claims (6)

A fuel pumping device including a high pressure pump (26) having an inlet connected to a low pressure fuel conduit (28) and an outlet connected to a main circuit for supplying high pressure fuel, and an electrical device (40) for starting the engine And an electrical starter cooling device connected to the pumping device to ensure cooling by fuel circulation,
The cooling device (54, 56, 58) has an inlet that is driven by an electric motor (52) independently of the high pressure pump (26) and connected to the pumping device upstream of the high pressure pump (26). An aero engine, characterized in that it is supplied with fuel by a pump (50) having it. The pumping device comprises a low pressure pump 24 driven from the shaft of the engine and having an outlet connected to the inlet of the high pressure pump (26);
The electric pump (50) supplying the cooling device has an inlet connected to the pumping device between the outlet of the low-pressure pump (24) and the inlet of the high-pressure pump (26). The listed aero engine.   3. An aircraft engine according to claim 1, characterized in that the electric pump (50) supplying the cooling device has an outlet connected to the main circuit (30) for supplying high pressure fuel. .   4. An aircraft engine according to claim 3, characterized in that the high-pressure pump (26) is a centrifugal pump.   A cooling device circulates fuel connected to a first circuit (54, 56) for circulating a heat transfer fluid connected to an electric starter and to an electric pump (50) supplying the cooling device. 4. A circuit according to claim 1, comprising: a second circuit (60) for heat and a heat exchanger (58) inserted through the first circuit and the second circuit. 5. Aircraft engine.   A cooling device is designed to cool the electric starter of the electric starter (40) and the electronic circuit (48) for controlling the electric power of the electric starter. An aero engine as described in any of the above.

Images